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<title>The C Preprocessor: Elif</title>

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<a name="Elif"></a>
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<hr>
<a name="Elif-1"></a>
<h4 class="subsection">4.2.5 Elif</h4>

<a name="index-_0023elif"></a>
<p>One common case of nested conditionals is used to check for more than two
possible alternatives.  For example, you might have
</p>
<div class="smallexample">
<pre class="smallexample">#if X == 1
&hellip;
#else /* X != 1 */
#if X == 2
&hellip;
#else /* X != 2 */
&hellip;
#endif /* X != 2 */
#endif /* X != 1 */
</pre></div>

<p>Another conditional directive, &lsquo;<samp>#elif</samp>&rsquo;, allows this to be
abbreviated as follows:
</p>
<div class="smallexample">
<pre class="smallexample">#if X == 1
&hellip;
#elif X == 2
&hellip;
#else /* X != 2 and X != 1*/
&hellip;
#endif /* X != 2 and X != 1*/
</pre></div>

<p>&lsquo;<samp>#elif</samp>&rsquo; stands for &ldquo;else if&rdquo;.  Like &lsquo;<samp>#else</samp>&rsquo;, it goes in the
middle of a conditional group and subdivides it; it does not require a
matching &lsquo;<samp>#endif</samp>&rsquo; of its own.  Like &lsquo;<samp>#if</samp>&rsquo;, the &lsquo;<samp>#elif</samp>&rsquo;
directive includes an expression to be tested.  The text following the
&lsquo;<samp>#elif</samp>&rsquo; is processed only if the original &lsquo;<samp>#if</samp>&rsquo;-condition
failed and the &lsquo;<samp>#elif</samp>&rsquo; condition succeeds.
</p>
<p>More than one &lsquo;<samp>#elif</samp>&rsquo; can go in the same conditional group.  Then
the text after each &lsquo;<samp>#elif</samp>&rsquo; is processed only if the &lsquo;<samp>#elif</samp>&rsquo;
condition succeeds after the original &lsquo;<samp>#if</samp>&rsquo; and all previous
&lsquo;<samp>#elif</samp>&rsquo; directives within it have failed.
</p>
<p>&lsquo;<samp>#else</samp>&rsquo; is allowed after any number of &lsquo;<samp>#elif</samp>&rsquo; directives, but
&lsquo;<samp>#elif</samp>&rsquo; may not follow &lsquo;<samp>#else</samp>&rsquo;.
</p>



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